Reversing mechanism for inboard-outboard boat drive

ABSTRACT

The reverse drive mechanism rotates a lower propulsion unit 180* from the forward drive position of said unit and eliminates the necessity for changing the direction of rotation of the propeller or propellers rotatably mounted in said unit. The reverse drive mechanism comprises gears built into the main drive mechanism, electrically controlled by an inboard control lever and timing device which automatically terminates rotation of the lower propulsion unit when the unit has been rotated 180* from its former propulsion position.

United States Patent 1191 Pinkerton 1 11 3,738,306 June 12, 1973 REVERSING MECHANISM FOR lNBOARD-OUTBOARD BOAT DRIVE Inventor: Lyle C. Pinkerton, 9264 Brighton Road, Henderson, Colo. 80640 Filed: June 18, 1971 Appl. No.: 154,467

U.S. c1. 115/35, 192/67 R, 192/84 R 1111.121 136311 5/12 Field 61 Search 115/35, 18 R, 18 E,

115/34 R, 4 1 R; 192/67 R, 84 R, 142 R, 99 s, 148, 70.2, 70.3, 93 A, 43.5

References Cited UNITED STATES PATENTS 3/1945 Billing 115/35 8/1956 Landerer 192/67 R West et al 192/148 3,603,437 9/1971 Spencer 192/148 Primary Examiner-Duane A. Reger Assistant Examiner-Barry L. Kelmachter Attorney-Bertha L. MacGregor [57] ABSTRACT The reverse drive mechanism rotates a lower propulsion unit 180 from the forward drive position of said unit and eliminates the necessity for changing the direction of rotation of the propeller or propellers rotatably mounted in said unit. The reverse drive mechanism comprises gears built into the main drive mechanism, electrically controlled by an inboard control lever and timing device which automatically terminates rotation of the lower propulsion unit when the unit has been rotated 180 from its former propulsion position.

9 Claims, 10 Drawing Figures PATENTEU 2 SHEETlBfS ATTORNEY PATENIEIJ m 2 W SHEHEBFS ATTORNEY PA'I'EIHED 3,738,306

SEEN 3 M 5 INVENTOR. LYLE C. PINKERTON ATTORNEY PAIEMTED Jim 2 m5 SHEET$W5 @QQHUH INVENTOR. LYLE C. PINKERTON ATTORNEY PAriminm 5.138.305

56 H 25 I I I (I /55 I 1 I I 13 28 INVENTOR. F g; MD LYLE C. P/NKERTON mi -MW ATTORNEY REVERSING MECHANISM FOR INBOARD-OUTBOARD BOAT DRIVE This invention relates to reversing mechanism for inboard-outboard boat drives.

The mechanism claimed herein may be embodied in drive mechanism disclosed in may co-pending application, Ser. No. 139,562 filed May 3, 1971, Inboard- Outboard Drive Mechanism for Boats, but is not limited to installation in said mechanism. The main object of the invention disclosed in my aforementioned copending application is toprovide an all gear drive mechanism to transmit power from one of more engines to a centrally located propulsion drive unit, with the capability of 360 steering and 180 lifting of a lower propulsion unit.

The main object of this invention is to provide reversing mechanism for rotating a lower propulsion unit including one or more propellers, for reversing the direction of travel of the boat, and to eliminate the necessity for changing the direction of rotation of the propellers for the purpose of reversing the direction of travel of the boat. Propellers designed for efficient propulsion of a boat in a forward direction are less efficient for propulsion of a boat in a rearward direction. By the use of my reversing mechanism, the same efficiency is attained for forward and rearward propulsion of the boat without reversing the direction of rotation of the propeller or propellers.

Another object of the invention is to provide reversing mechanism built into the drive mechanism, designed to avoid interruption and reversal of the drive gear train also shown and described herein.

Another object of the invention is to provide an inboard control lever for actuating the reverse mechanism, and timing mechanism by which the rotation of the lower propulsion unit is terminated automatically when the unit has been rotated 180 from its former propulsion position.

Other objects and advantages will become apparent from the following description and the drawings.

In the drawings:

FIG. 1 is an elevational side view of the stern portion of a boat on which is mounted the inboard-outboard propulsion and reversing mechanism embodying my invention, showing the lower propulsion unit in its forward drive position in full lines and in its rearward drive position in broken lines.

FIG. 2 is a top view of the same.

FIG. 3 is an elevational vertical rear view, partly in section, with the outer housing partially omitted, of the central sections of the drive mechanism, showing the lower propulsion unit housing and propellers turned 90 from their straight forward drive positions.

FIG. 4 is a view similar to FIG. 3, on an enlarged scale, of the upper central section and lesser portions of adjacent side sections, with the lower propulsion unit omitted, showing in section some of the parts shown in elevation in FIG. 3.

FIG. 5 is a top plan view, with the top of the outer housing omitted, on the same scale as FIG. 4, showing the propulsion and reversing mechanism, with the engine driven drive shafts broken away.

FIG. 6 is a horizontal sectional view of a detail of construction in the plane of the line 6-6 of FIG. 4.

FIG. 7 is an elevational view, partly in section, of the timing mechanism associated with the reversing and i steering means, showing the timing gear out of engagement with the steering shaft.

FIG. 8 is a view similar to FIG. 7 showing the timing mechanism in engagement with the steering shaft.

FIG. 9 is an elevational view showing the connection means between the timing mechanism and the solenoid which controls the mechanism for reversing the position of the lower propulsion unit.

FIG. 10 is an elevational view of means for latching the propulsion unit to the boat.

For purposes of disclosing the reversing mechanism of my invention by which the forward and rearward direction of travel of the boat is controlled, I have chosen to show and describe the same as embodied in the drive mechanism of my co-pending application aforementioned, but it is to be understood that the said reversing mechanism can be built into other propulsion means without departing from the scope of this invention.

In the embodiment of the invention shown in the drawings, a boat 10 has a transom 11 on which the outboard upper part 12 of the propulsion unit is mounted, with the lower or propeller unit 13 depending therefrom. Inboard parts of the mechanism include two engines 14, 15, a motor 16, steering control wheel 17, flexible steering shaft 18, and timing mechanism housing 19 containing parts shown in FIGS. 7 and 8, to be described hereinafter. Other inboard parts are the reverse control lever 20 and lead 21.

The propulsion unit 12 comprises a housing having a central section 25 and adjacent end sections 26, 27, partly integrally formed. The central section 25 consists of a transom-contacting wall, with the top, front and bottom cut away to permit rotation of an inner central housing. As shown in FIG. 5, the central section includes an inner housing 28 which is rotatable and concentric with the inturned flange members 29, 30, on the housing sections 26, 27, respectively. Seals 31 and roller bearings 32 are located between the flange 29 and inner housing 28, and between the flange 30 and housing 28. This construction facilitates relative rotary movement between the inner housing 28 and the stationary housings 26, 27, for the purpose of lifting the propeller unit portion of the mechanism.

The engine 14 is operatively connected to drive mechanism hereinafter described by a horizontal rotatable shaft 35, and engine 15 is operatively connected to the said drive mechanism by a horizontal rotatable shaft 36. The shafts extend through the housing sections 26, 27, respectively, as shown in FIG. 5. The motor 16 is operatively connected to propeller unit lifting mechanism, by a horizontal shaft 37 (FIG. 5) which extends through the housing 26 in a location adjacent the central section housing 28 where it functions to rotate and operate means for pivotally lifting the housing 28 and contents.

Referring now to the propulsion unit drive mechanism in the housing members 25, 26, 27, as shown in FIGS. 3-5, a hollow horizontal idler shaft 40 is mounted at each end in a bearing support 41 and hanger 42, the latter being fastened to the housings 26 and 27, respectively, by retaining bolts 43. The idler shaft 40 is supported by the two stationary housings, 26, 27, and carries the operative drive mechanism without any stress on the movable housing 28 and its contents. The idler shaft 40 is provided with an extrusion 44 in the form of a collar having an internal diameter larger than the external diameter of the shaft 40 for reception of an upper reverse dog gear 45, upper bearing 46 and lower bearing 47 (FIG. 4), said bearing members being located between the extrusion 44 and reverse dog gear 45. A retaining ring 48 is located between the bearing members 46, 47, and the extrusion 44 on shaft 40. The extrusion 44 forms a housing and retainer for the bearing members.

A vertical main propulsion shaft 50 extends through the reverse dog gear 45, which has splined on its upper end a power accumulating gear 51 retained by a snap ring 52. The reverse dog gear 45 is loose on the vertical shaft 50.

The power accumulating gear 51 has rotary motion transmitted to it through the following mechanism: engine shaft rotates pinion 53 and simultaneously engine shaft 36 rotates pinion 54; pinion 53 meshes with and drives power transfer gear 55 loose on shaft while simultaneously pinion 54 drives power transfer gear 56 which is loose on shaft 40; power transfer gear engages a one-way rolling clutch assembly 57 while simultaneously power transfer gear 56 engages one way rolling clutch assembly 58; rolling clutch assembly 57 when in locked position transmits rotary motion to transfer gear 59 while simultaneously rolling clutch assembly 58 when in locked position transmits rotary motion to transfer gear 60. The gear train 55-60 is loosely mounted on idler shaft 40 and sustained on the idler shaft with suitable bearings to allow the gear train to rotate freely. Gears 59 and 60 mesh with and rotate the power accumulating gear 51 which rotates the dog gear 45 loosely mounted on vertical drive shaft 50. Thrust bearings for both transfer gears 59, 60 are designated 61.

The power accumulating gear 51, splined over the upper reverse dog gear 45, retains the gear 45 and bearings 46, 47 in the extrusion 44 of the idler shaft 40. A dog clutch is splined onto the vertical drive shaft 50. When the clutch 65 is in driving engagement with the power accumulating gear 51, as shown in FIG 4, the vertical shaft 50 is rotated and transmits rotary motion through gear 66 fixedly mounted on the lower end of shaft 50 to the propeller drive gears 67, 68 fixedly mounted on propeller shafts 69, 70, respectively, to drive propellers 71, 72, respectively, in counter rotation.

The dog clutch 65 is moved into or out of driving engagement with the power accumulating gear 51 by the following described mechanism: A clutch control lever extends inwardly through the transom 1 1 and is provided with a clutch control actuating ball 76 on its outboard end. Between its ends the lever 75 is mounted in a retaining ring 77. The clutch control actuating ball 76 engages a clutch plate 78 to rotate the plate, causing the clutch actuating rollers 79 in tapered slots to be forced against a clutch actuating plate 80 to thereby push the plate 80 away from the clutch 65. This movement applies outward pressure or pulling motion on the shifting fork actuating arm 81 which is pivotally connected at 82 to an ear on the shifting fork 83. The shifting fork 83 engages the clutch 65 to lower it into engagement with the power accumulating gear 51 as shown in FIG. 4 to transmit driving motion to the vertical shaft 50. The shifting fork actuating arm 81 is provided with a roller 84 which moves in an annular slot cast in the clutch actuating plate 80.

When the shifting fork 83 is raised, the clutch 65 is moved out of engagement with gear 51 in nontransmitting position. This is its position when disengagement is desired between the engine and the propulsion unit.

The means for reversing the direction of thrust of the propeller unit and controlling the direction of travel of the boat comprises the control lever 20 and the aforementioned upper reverse dog gear 45 which is loose on the vertical drive shaft 50 and has splined on its upper end the power accumulating gear 51 retained by the snap ring 52. When moved to rearward position, the control lever 20 actuates a two-way switch (not shown) which feeds electrical current to a solenoid 85 (located to the left of the vertical drive shaft as best shown in FIG. 4) and to a solenoid 112 which is part of the timing mechanism shown in FIGS. 7 and 8. The reverse actuating solenoid 85 actuates a mutilated gear 86 which meshes with teeth on a clutch plate 95 (FIGS. 6 and 4). The gear 86 is mounted on a pin 87 suitably supported in idler shaft 40. The solenoid 85 is electrically connected to the timing mechanism by leads 88 as shown in FIGS. 7-9.

Below the upper reverse dog gear 45 is a lower reverse dog gear 90 splined over a sleeve 91. The sleeve 91 is splined into a multiple clutch arrangement 92. The latter is retained between the sleeve 91 and a clutch plate 93 splined into the lower unit housing 94. The said housing 94 is screwed into a steering gear referred to hereinafter as 102 and retained by a splined sleeve 103. The lower reverse dog 90 is moved into engagement with the upper reverse dog gear 45 by means comprising the clutch plate 95 rotating on ball bearings 96 retained in tapered slots in the clutch plate 95, which apply upward pressure on the lower reverse dog gear 90 and thereby force it upwardly into contact with the upper dog gear 45. Thus power delivered through the upper dog gear 45 rotates the lower unit housing 94. Rotation of the lower unit housing 94 is terminated by the action of the timing wheel 114 described hereinafter which trips a two-way switch 22 thus deenergizing electrical solenoids 85 and 112, allowing return spring 97 to force the lower dog gear 90 downwardly and disengaging from the upper dog gear 45. At the same time, the return spring 116 forces the timing clutch gear 113 onto the splines of the steering wheel shaft 1 10.

The lower unit housing 94 and parts associated therewith are rotated for two purposes: reversing and steering. For steering, power is conveyed through the steering wheel 17 and flexible shaft 18, the latter including interconnected ends and mechanism shown in FIGS. 7 and 8 to be described in detail hereinafter. Power is applied to a steering shaft and gear 100 located in the housing 27; the shaft and gear 100 rotate a transfer gear 101 rotatably mounted on a pin projecting from idler shaft 40 as shown in FIG. 4. Steering transfer gear 101 rotates the steering gear 102. Steering gear 102 is firmly fastened to the lower unit housing 94 through a threading arrangement and firmly retained by a splined collar 103. The collar 103 is prevented from upward movement by a spring 104. As the steering wheel 17 is rotated, the lower unit 94 and parts carried thereby are rotated for directional control of the boat.

As shown in FIGS. 7 and 8, the flexible shaft 18 has a splined end operatively connected to the shaft 111 connected to steering shaft and gear 100. The operative connection between the splined end 110 and shaft 111 comprises the timing clutch gear 113 on said splined end 110 of the shaft 18, said clutch gear 113 being actuated by the lever 117 and engaging the return spring 1 16 on said shaft 1 1 1. At the same time that electrical current is fed to the reverse actuating solenoid 85, current also is fed to a timing gear solenoid 112 which causes the lever 117 to move the timing clutch gear 113 to engage the timing gear 114 and thus disengage it from the splined shaft 110. As the lower unit 94 rotates, negative motion is fed from the steering gear 102 to the steering transfer gear 101 to the steering pinion gear and shaft 100 and into the flexible shaft 111 to timing clutch gear 113, causing the timing gear 114 to be rotated in an annular path. The timing gear is so designed that when the lower unit has rotated l80, the timing gear 114 has completed a 360 rotation. The timing gear has a protruding lip 115 which on completion of one revolution trips the two way switch 22, thus opening the electric circuit and allowing the electric solenoids 85 and l 12 to become deactivated, which allows the return spring 116 to force the timing clutch gear 113 onto the splines of the steering wheel shaft 110 to return to normal steering. At this same time, return spring 96 forces the lower reverse dog gear 90 downward, disengaging the dog gears 45 and 90 and stopping rotation of the lower unit 94.

From the foregoing, the operation of the drive and reversing mechanism will be understood as follows:

Power from the engines 14 and 15, or one of them, will be transmitted through gearing train or trains to the power accumulating gear 51 which, through gear 65, rotates the vertical drive shaft 50 and propeller unit including propellers 71 and 72 or one of them. This is the normal forward drive arrangement. For propelling the boat in rearward direction, the reverse mechanism is actuated by moving the inboard control lever 20, thereby activating solenoid 85 through the electrical leads 21, timing device 19 and electrical lines 88. The solenoid 85 when energized actuates the mutilated gear 86 which meshes with clutch plate 95. The latter transmits upward pressure on the lower reverse dog gear 90 to force it upwardly into contact with the upper dog gear 45 rotated by gear 51. Power transmitted through the upper dog gear 45 rotates the lower propulsion housing 94 (through sleeve 91, multiple clutch 92 and clutch plate 93). Rotation of the lower unit housing 94 is automatically terminated by the timing wheel 114 which trips the two way switch 22 and de-energizes the electrical solenoids 85 and 112 when the lower unit has been rotated 180 from its forward-travel position, allowing return spring 97 to force the lower reverse dog gear 90 downwardly and disengaging it from the gear 45. At the same time the return spring 116 forces the timing clutch gear 113 onto the splines of steering wheel shaft 110 which has been disengaged during the operation of the reverse mechanism.

Thus the lower housing 94 and the propeller unit housed therein are turned bodily 180 into position for reverse or rearward propulsion of the boat without interruption of the drive gear train or trains and without reversing the direction of rotation of the propellers from their forward drive direction of thrust.

Some details of construction not heretofore numerically designated include the following: suitable bearings 130 for engine shafts 35, 36, in housings which are part of the housing sections 26, 27, bearings 131 for the motor shaft 37 in a housing which is part of the housing section 25, and drain plugs 132 in housing sections 26,

27, as shown in FIG. 5. In FIGS. 3 and 4 are shown threaded plugs 133 in the central housing 28 which are removable to facilitate insertion, one by one, of the ball bearings 32 between the central housing 28 and flanges 29 and 30, respectively, of the stationary housing sections 26, 27. Guide arms 134 extend rearwardly from the stationary housings 26, 27, for housing latching and trim mechanism described in a separate application. Various bearings and springs are shown without numerical designations, their functions being obvious.

Latching means for latching the housing 28 to the boat comprise a latch member 135 for engaging a bolt or pin 136 on the boat provided for preventing unintended lifting of the lower propulsion unit in operation of the boat.

Means for lifting the lower housing 94 and propellers mounted therein will be the subject of a separate appli cation. The parts are designated herein as motor 16, motor shaft 37, worm 120, worm release spring 121, worm retaining collar 122, thrust bearing 123, and worm ring gear 124. These parts do not affect the operation of the reverse mechanism and therefore need not be described herein in detail.

I claim:

1. Reversing mechanism for reversing the direction of travel of a boat without interrupting its drive means by altering the direction of thrust of its propeller or propellers comprising a. a main housing for mounting on the stern of a boat,

b. a lower housing rotatably mounted in the main housing,

c. a power rotated vertical drive shaft mounted in the main housing and extending into said lower housd. a propeller unit mounted in the lower housing operatively connected to said vertical drive shaft for propelling the boat,

e. a lever controlled solenoid,

f. an upper dog gear and a lower dog gear mounted on the vertical drive shaft,

g. operative connection between the solenoid and the lower dog gear for moving said gear into and out of driving connection with the upper dog gear, and

h. operative connection between said upper dog gear and the lower housing for rotating said housing and moving the housing and propeller unit into reverse position.

2. The reversing mechanism defined by claim 1, which includes timing means automatically terminating rotation of the lower housing when it has been turned from its former drive position.

3. The reversing mechanism defined by claim 2, in which the timing means comprises a solenoid electrically connected to the lever controlled solenoid, a timing wheel and a clutch gear, the said clutch gear being moved by the timing means solenoid into or out of engagement with the timing wheel to thereby trip a two way switch to de-energize the lever controlled solenoid when the timing wheel has been rotated 360.

4. The reversing mechanism defined by claim 1, in which said upper dog gear is rotated by a power rotated accumulator gear and said lower dog gear is slidable on the vertical drive shaft.

5. The reversing mechanism defined by claim 4, in which the operative connection between the solenoid and the lower dog gear comprises a mutilated gear meshing with a clutch plate rotating on ball bearings retained by tapered slots in said clutch plate to apply upward pressure on the said lower dog gear to force it upwardly into contact with the upper dog gear.

6. The reversing mechanism defined by claim 4, in which the operative connection between the upper dog gear and said lower housing for rotating said lower housing when the upper and lower dog gears are in engagement with each other comprises said lower dog gear splined over a sleeve which is splined into a multiple clutch arrangement retained between said sleeve and a clutch plate splined into the said lower housing.

7. In combination with a boat, reversing mechanism for reversing the direction of travel of the boat without interrupting its drive means by altering the direction of thrust of its propeller or propellers comprising a. a main housing for mounting on the stern of a boat,

b. a lower housing rotatably mounted in the main housing,

c. a power rotated vertical drive shaft mounted in the main housing and extending into said lower housing,

d. a propeller unit mounted in the lower housing operatively connected to said drive shaft for propelling the boat,

e. an inboard reverse control lever,

f. a solenoid electrically connected to the control lever, said solenoid being located in the main housing,

g. a pair of gears mounted on the vertical drive shaft,

one of said gears being an upper dog gear loosely mounted on the vertical drive shaft and rotated by an engine powered gear, and the other of said gears being a lower dog gear slidable on the vertical drive shaft into and out of engagement with the upper dog gear,

h. operative connection between the solenoid and said slidable lower dog gear for moving said gear into engagement with the upper dog gear, and

i. operative connection between the upper dog gear and said lower housing for rotating said housing and moving the housing and propeller unit into reverse position without interrupting the driving rotation of the drive shaft.

8. The reversing mechanism defined by claim 7, in which the operative connection between the solenoid and said slidable lower dog gear comprises a mutilated gear meshing with a clutch plate rotating on ball bearings retained by tapered slots in said clutch plate to apply upward pressure on the said lower dog gear to force it upwardly into contact with the upper dog gear.

9. The reversing mechanism defined by claim 7, in which the operative connection between the upper dog gear and said lower housing comprises said lower dog gear splined over a sleeve which is splined into a multiple clutch arrangement retained between said sleeve and a clutch plate splined into the said lower housing. 

1. Reversing mechanism for reversing the direction of travel of a boat without interrupting its drive means by altering the direction of thrust of its propeller or propellers comprising a. a main housing for mounting on the stern of a boat, b. a lower housing rotatably mounted in the main housing, c. a power rotated vertical drive shaft mounted in the mAin housing and extending into said lower housing, d. a propeller unit mounted in the lower housing operatively connected to said vertical drive shaft for propelling the boat, e. a lever controlled solenoid, f. an upper dog gear and a lower dog gear mounted on the vertical drive shaft, g. operative connection between the solenoid and the lower dog gear for moving said gear into and out of driving connection with the upper dog gear, and h. operative connection between said upper dog gear and the lower housing for rotating said housing and moving the housing and propeller unit into reverse position.
 2. The reversing mechanism defined by claim 1, which includes timing means automatically terminating rotation of the lower housing when it has been turned 180* from its former drive position.
 3. The reversing mechanism defined by claim 2, in which the timing means comprises a solenoid electrically connected to the lever controlled solenoid, a timing wheel and a clutch gear, the said clutch gear being moved by the timing means solenoid into or out of engagement with the timing wheel to thereby trip a two way switch to de-energize the lever controlled solenoid when the timing wheel has been rotated 360*.
 4. The reversing mechanism defined by claim 1, in which said upper dog gear is rotated by a power rotated accumulator gear and said lower dog gear is slidable on the vertical drive shaft.
 5. The reversing mechanism defined by claim 4, in which the operative connection between the solenoid and the lower dog gear comprises a mutilated gear meshing with a clutch plate rotating on ball bearings retained by tapered slots in said clutch plate to apply upward pressure on the said lower dog gear to force it upwardly into contact with the upper dog gear.
 6. The reversing mechanism defined by claim 4, in which the operative connection between the upper dog gear and said lower housing for rotating said lower housing when the upper and lower dog gears are in engagement with each other comprises said lower dog gear splined over a sleeve which is splined into a multiple clutch arrangement retained between said sleeve and a clutch plate splined into the said lower housing.
 7. In combination with a boat, reversing mechanism for reversing the direction of travel of the boat without interrupting its drive means by altering the direction of thrust of its propeller or propellers comprising a. a main housing for mounting on the stern of a boat, b. a lower housing rotatably mounted in the main housing, c. a power rotated vertical drive shaft mounted in the main housing and extending into said lower housing, d. a propeller unit mounted in the lower housing operatively connected to said drive shaft for propelling the boat, e. an inboard reverse control lever, f. a solenoid electrically connected to the control lever, said solenoid being located in the main housing, g. a pair of gears mounted on the vertical drive shaft, one of said gears being an upper dog gear loosely mounted on the vertical drive shaft and rotated by an engine powered gear, and the other of said gears being a lower dog gear slidable on the vertical drive shaft into and out of engagement with the upper dog gear, h. operative connection between the solenoid and said slidable lower dog gear for moving said gear into engagement with the upper dog gear, and i. operative connection between the upper dog gear and said lower housing for rotating said housing and moving the housing and propeller unit into reverse position without interrupting the driving rotation of the drive shaft.
 8. The reversing mechanism defined by claim 7, in which the operative connection between the solenoid and said slidable lower dog gear comprises a mutilated gear meshing with a clutch plate rotating on ball bearings retained by tapered slots in said clutch plate to apply upward pressure on the said lower dog gear to force it upwardly into contact with the upper dog gear.
 9. The reversing mechanism defined by claim 7, in which the operative connection between the upper dog gear and said lower housing comprises said lower dog gear splined over a sleeve which is splined into a multiple clutch arrangement retained between said sleeve and a clutch plate splined into the said lower housing. 